I was joking, but that was the model I had in mind - although the competence and capability gap between the UK Rangers and the US SMUs is huge, of course, as you say, what we're putting together doesn't look unlike a USSF SF Group. I suppose each of the new small battalions could put together A, B and C Teams and, given the right training and selection for aptitude, produce the necessary specialists to fit the various slots in an A Team.You joke, but this isn't far off how the US runs things. Their SMUs are commanded one level up, so the CO slot is a brigade level command and the squadrons are battalion level commands. Their green beret battalions (theoretically doing the job were asking the rangers to do, more or less) have their own CO but are all sat within groups, each with a brigade level commander. There are, incidentally, four battalions per group.... Above that is the divisional level command, and above that is USASOC which commands at the corps level. None of those, less the battalion commanders, have any J3/5 function - that's executed by the COCOMs. All three levels of command outline above are responsible for J1, 4, 7, 8 and 9.
@Alamo is definitely right here. I agree with other posters that the British army has far too many unnecessary HQs (6XX and the Field Army for example) but the ranger HQ isn't one of them. There needs to be some kind of C2 function over those battalions. That doesn't mean it needs to be scaled as a deployable brigade HQ.